Fragile X Syndrome (FXS) is a genetic cognitive disorder characterized by intellectual impairment, social inhibition, and physical abnormalities and is the leading inheritable cause of Autism Spectrum Disorder. A cytosine-guanine-guanine trinucleotide repeat expansion mutation in the FMR1 gene promoter leads to the loss of expression of the Fragile X Mental Retardation Protein (FMRP) during neuronal development. FMRP contains two types of RNA binding domains including two K Homology domains and one arginine-glycine-glycine (RGG) box. The RGG box has been previously shown to bind to a specific RNA secondary structure known as a G-quadruplex. G-quadruplexes form in guanine-rich nucleic acid sequences and are structurally comprised of 2-4 stacks of planar guanine quartets, stabilized by Hoogsteen base-pairing. FMRP has been shown to bind to the messengerRNA (mRNA) encoding for the DROSHA protein, an RNAse III enzyme vital to primary microRNA processing in the nucleus. DROSHA regulation via FMRP may be a way to regulate the microRNA pathway, however, the binding mechanism between FMRP and Drosha mRNA is unclear. Drosha mRNA contains a guanine-rich region that has the potential to form a G-quadruplex in its 5' untranslated region (UTR). In this study, we used biophysical techniques such as 1H NMR, circular dichroism, UV-vis, and steady-state fluorescence spectroscopies and native PAGE to determine the ability of the guanine rich region in the 5' UTR of Drosha mRNA to form a G-quadruplex structure in vitro and to demonstrate the binding between this structure and FMRP.

Investigating the binding mechanism between FMRP and Drosha mRNA G-quadruplex

255th National Meeting (2018)

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